Interpretive Summary: Because of problems with the development of resistance to conventional pesticides, there is a critical need for new concepts and alternative approaches in controlling insect pests. The basic premise of this research is that neuropeptides (short chains of amino acids) serve as potent messengers in insects to regulate vital functions. New, selective control measures may be developed by designing metabolically stable mimics of these neuropeptides that actively inhibit or over-stimulate functions regulated by them, resulting in disruption of the internal environment of the insect. We report on a comparison of the activity of native peptides to elicit the transformation of an immature stage of the flesh fly to the adult form. In addition, the effects of these peptides on the underlying muscular patterns that accompany this maturation process were studied in detailed fashion via a specialized technique that monitors changes in internal pressure. A deeper understanding of how these neuropeptides regulate critical processes in insects will aid in the design of strategies to disrupt insect maturation. The work brings us one step closer to the development of practical neuropeptide-like substances that will be effective in controlling pest insects in an environmentally friendly fashion.

Technical Abstract:
MALDI-TOF-TOF tandem mass spectrometry has been applied to determine the complete sequences of the PVK/CAP2b neuropeptides in the stable fly Stomoxys calcitrans and horn fly Haematobia irritans, insect pests of livestock. This peptidomic analysis of single neurohemal organ preparations allows the unambiguous assignment of internal Leu/Ile positions not distinguishable by previous mass spectrometric techniques. The sequences are as follows: Stoca-PVK/CAP2b-1, AGGASGLYAFPRVa; Stoca-PVK/CAP2b-2, NAKLYPVPRVa; and Haeir-PVK/CAP2b-1, AGGASGLYAFPRVa; Haeir-PVK/CAP2b-1, NAKLYPMPRVa. Both Stoca-PVK/CAP2b-1 and -2 stimulate Malpighian tubule fluid secretion in the stable fly, with EC50 values between 3 and 11 nm. The identification of these novel neuropeptides adds to our knowledge of the peptidomes of flies, and can aid in the development of neuropeptide-based control strategies of these insect pests.